Patent FR-A-2499034, filed on Nov. 14, 1980, describes a rotational device for redirecting bottles or similar articles coming from a conveyor line towards other conveyor lines. The device comprises a rotor formed by an upper plate and a lower plate which are superimposed, separated and connected to rotate together with respect to a vertical axis. Upper indentations are formed in a perimetric edge of the upper plate and lower indentations are formed in a perimetric edge of the lower plate, such that the mentioned upper and lower indentations, which are vertically aligned, form a plurality of receiving configurations uniformly distributed along the periphery of the rotor to be coupled with the bottles. Between the two plates there is arranged a plurality of outwardly facing suction cups, and each suction cup is in a position corresponding to one of the mentioned receiving configurations. The suction cups are connected by respective conduits to a negative pressure chamber formed in the hub of the rotor, and the negative pressure chamber is in communication with a vacuum source through a rotary joint. A valve is arranged in each of the mentioned conduits, and when the rotor rotates, the valves are selectively opened along a circumferential arc and closed again by cams fixed in a static support. When a valve is opened, the corresponding suction cup experiences a depression capable of holding by suction a bottle against the receiving configuration of the rotor along said circumferential arc. When the valve is closed again, the bottle is released onto another conveyor line.
Patent JP-A-58172109, filed on Apr. 5, 1982, discloses a device for removing defective bottles from a bottle conveying line in response to a signal generated by inspection means. The device comprises a rotor having a construction that is very similar to that described in the mentioned patent FR-A-2499034, except in that here each suction cup is in communication through a conduit with a corresponding hole formed in the lower plate. The lower plate rotates in frictional contact on a stationary fluid distribution plate where there are formed elongated holes connected with a vacuum source through conduits and electrically controlled valves which are selectively opened and closed according to said signal generated by the inspection means. When the rotor rotates, each suction cup can be put in communication with the fluid source when the corresponding hole of the lower plate of the rotor passes over one of the elongated holes of the stationary distribution plate to hold the bottle to the corresponding receiving configuration of the rotor and when one of the mentioned valves is opened.
A drawback of the use of suction cups is that for the operation thereof a type of vacuum at a relatively low relative pressure and a relatively small flow rate is necessary, which is typically obtained by means of a vacuum pump associated to a vacuum tank, which involves relatively high installation and maintenance economic costs. Furthermore, the need to provide a suction cup with its corresponding arrangement of conduits associated to each receiving configuration makes the construction of the rotor complex and increases the economic costs thereof.
Patent EP-A-1594781, with Italian priority of Feb. 19, 2003, describes a rotational conveyor for introducing or extracting empty plastic bottles or containers into or from a positioning machine. The conveyor comprises a rotor formed by separated upper and lower plates, and a plurality of indentations uniformly distributed along the periphery of said two plates, such that the indentations of the upper plate are vertically aligned with the indentations of the lower plate forming receiving configurations to be coupled with the bottles. Each receiving configuration is equipped with a box-like element supported by the lower plate, and each of said box-like elements has a vertical opening made in an outer wall following the concave profile of the corresponding receiving configuration. Horizontal openings are formed in the lower plate, each of which is in communication with one of the box-like elements. The mentioned horizontal openings are arranged along a circumference which is superimposed on an elongated curvilinear slot defined in a stationary chamber in which a negative pressure is created, said elongated slot extending along a predetermined circumferential arc. Thus, when, upon the rotation of the rotor, each horizontal opening passes above the elongated slot, the corresponding box-like element is in communication with the negative pressure chamber and a suction occurs through the vertical opening of the corresponding receiving configuration along the mentioned circumferential arc, said suction being sufficient to hold the empty bottle against the surface of the receiving configuration.
A drawback of this rotational conveyor is that it needs a box-like element associated to each receiving configuration to carry out a function similar to that of the suction cups in the aforementioned documents, and the need to provide a large number of box-like elements makes the construction of the rotor relatively complex and expensive. Furthermore, the receiving configurations of the rotor are adapted for a single bottle format, and providing a different rotor for each bottle format is not cost-effective.
International patent application WO 2007/031239, with Italian priority of Sep. 12, 2005, describes a rotational conveyor with a construction very similar to that of the mentioned patent EP-A-1594781, with the difference that the rotor comprises a plurality of interchangeable receiving elements, each of said receiving elements having a receiving configuration and a vertical opening which is in communication with the corresponding box-like element when the receiving elements is installed in the rotor. The receiving elements have quick connection means for the connection with the upper and lower plates of the rotor. This allows having different sets of receiving elements adapted for different bottle formats. A drawback is that when the rotor is to be adapted to bottles or containers of a different format, a large number of receiving elements of a first type must be uninstalled to then install a large number of receiving elements of a second type, and this operation requires time and is not cost-effective.
Document DE-A-102006055963 discloses a rotary device for transferring objects comprising a rotor having a thick perimetric wall with a plurality of receiving configurations uniformly distributed along its periphery for receiving said objects and conduits through said thick perimetric wall communicating said receiving configurations with a cylindrical inner surface of the thick perimetric wall. Rotation means are provided to make said rotor rotate. A stationary negative pressure chamber connected to a suction source is formed inside the rotor, and said negative pressure chamber is partly delimited by said cylindrical inner surface of the thick perimetric wall of the rotor along a predetermined circumferential arc, such that suction is provided through said conduits to each receiving configuration to hold by suction one of the objects in the receiving configuration along said predetermined circumferential arc.
A drawback with said rotary device is that the conduits communicating the negative pressure chamber with the receiving configurations cause a significant pressure loss due to the small diameter of the conduits with regard the dimensions of the receiving configurations and to the long length thereof due to the large thickness of the perimetric wall. Another drawback is that the thick perimetric wall makes the rotor heavy and difficult to be handled for installing and uninstalling it to and from the device. Still another drawback is that the rotor with the receiving configurations and the conduits has to be obtained by mechanizing a thick block of material, which makes the rotor expensive to be manufactured. The above drawbacks are made worse when the rotor is intended to handle articles of relative big size, such as bottles or containers, instead of small objects such as the preforms described in all the embodiments of cited document DE-A-102006055963.